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      02-01-2012, 09:31 PM   #1
bigblackwolf
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Recently I read about the Volkswagen Cross Coupe concept, and that looks like the kind of technology I would like to have in a future X3.
http://www.topspeed.com/cars/volkswa...-ar120772.html
My interest is based on the following two factors in present technology:
- fuel consumption. When driving the X3 which shows the instantanious fuel consumption, I realize that fuel consumption is very high during acceleration and going uphill, but this energy cannot be recovered well when slowing down or going downhill.
- Mechanical all wheel drive with driveshafts splitting up to all wheels and varying traction control is very sophisticated, but also complex.

The Cross Coupe concept looks simple and neat:
- engine drives front wheels
- electric motors/generators on the rear wheels can provide all-wheel-drive and energy recovery.
- the electric motors can assist acceleration. Electric motors have a high torque to power ratio, which would be beneficial to assist acceleration of a downsized engine, further reducing fuel consumption.
What I do not care so much about at this stage is all electric drive and pluginhybrid.

Other examples of this concept are: Lexus RX450h, Peugeot 3008 and Citroen DS5 Hybrid4.

Last edited by bigblackwolf; 02-01-2012 at 09:43 PM..
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      02-01-2012, 10:23 PM   #2
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Screw hybrids

The total lifetime cost makes no sense (according to the figures I've seen). Give me a good diesel any day as a much better option.
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      02-01-2012, 10:43 PM   #3
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I agree with LeChef. Diesel option would be way better in terms of torque, fuel economy and overall savings.

However, I think the OP is requesting a system that is currently being tested and will be employed in the BMW i brand where electronic motors are driving the front wheels and engine back, eliminating the need for drive shafts. Essentially electronic awd system. Honda/Acura has also been testing this set up.

*incase u didn't catch on... BMW has been working on this before the VW group.
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      02-01-2012, 11:41 PM   #4
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Quote:
Originally Posted by Le Chef View Post
The total lifetime cost makes no sense (according to the figures I've seen). Give me a good diesel any day as a much better option.
I am not talking about just adding hybrid to an existing car, because that is expensive, but about engine downsizing and eliminating mechanical all-wheel drive, and then adding hybrid.

Audi Q5 has options for different engines, all-wheel-drive and hybrid. So let us look what it costs (price list from Germany).

Cost saving:
Engine downsize and eliminate all-wheel-drive: compare 6-cylinder 3.0TDI quattro 49'200Euro (torque 500Nm) with 4-cylinder 2.0TDI 34'850Euro (torque 320Nm).
Saving: about 14'000Euro.

Additional hybrid cost:
Compare 2.0 TFSI quattro 43'900Euro with 2.0TFSI quattro hybrid 53700Euro. Electro motor has a torque of 210Nm.
Additional cost: 10'000Euro.

So in total, there is still a saving, and the torque loss of the engine downsizing is compensated by the electric motor torque.
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      02-01-2012, 11:54 PM   #5
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Quote:
Originally Posted by bigblackwolf View Post
Recently I read about the Volkswagen Cross Coupe concept, and that looks like the kind of technology I would like to have in a future X3.
http://www.topspeed.com/cars/volkswa...-ar120772.html
My interest is based on the following two factors in present technology:
- fuel consumption. When driving the X3 which shows the instantanious fuel consumption, I realize that fuel consumption is very high during acceleration and going uphill, but this energy cannot be recovered well when slowing down or going downhill.
- Mechanical all wheel drive with driveshafts splitting up to all wheels and varying traction control is very sophisticated, but also complex.

The Cross Coupe concept looks simple and neat:
- engine drives front wheels
- electric motors/generators on the rear wheels can provide all-wheel-drive and energy recovery.
- the electric motors can assist acceleration. Electric motors have a high torque to power ratio, which would be beneficial to assist acceleration of a downsized engine, further reducing fuel consumption.
What I do not care so much about at this stage is all electric drive and pluginhybrid.

Other examples of this concept are: Lexus RX450h, Peugeot 3008 and Citroen DS5 Hybrid4.
In college I was on the Formula Hybrid team for 4 years and in my 4th year I lead the team and designed a hybrid gas-electric powertrain. This powertrain was no where near as sophisticated as a production car powertrain and was oriented for racing (with constraints around the competition rules). However, I feel like I have a pretty good understanding of the benefits and drawbacks of production style hybrid powertrains.

The future means more and more electric power and less and less gas power. The ratio of the two found in cars will be biased with the relative energy density of gasoline versus batteries (or whatever new technology comes along). The more energy dense the electrical storage becomes the more electric biased cars will become.

Right now batteries are heavy and bulky and the vehicle integration is poor. It is getting a lot better (and for some cars - very good).

There are a lot of advantage to the electric rear - gasoline front design. You can eliminate a drive shaft but retain rear-wheel drive characteristics, you can use the electric motor to bias torque in the rear wheels to combat over / under yaw moment in a more productive manner, you can still regen since your engine is still coupled to the ground "through the road".

However, I'm just not convinced it is a good solution. You don't eliminate the exhaust which means you still have a tunnel going through your chassis not improving chassis stiffness or vehicle safety. You can't really regain that much energy through regen in the rear wheels or with a weak electric motor. Your weight is going to go through the roof and your passenger volume decreases because of the batteries. Most importantly... you loose the ability to apply most of your power to the rear wheels and have a more sporty like experience. Ohh yeah... the price is going to climb a bunch too!

As has been stated, a turbo diesel with start / stop capability seems like a better solution! But heck - the X3 gets pretty good gas mileage.
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      02-02-2012, 12:00 AM   #6
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Quote:
Originally Posted by bigblackwolf View Post
Recently I read about the Volkswagen Cross Coupe concept, and that looks like the kind of technology I would like to have in a future X3.
http://www.topspeed.com/cars/volkswa...-ar120772.html
My interest is based on the following two factors in present technology:
- fuel consumption. When driving the X3 which shows the instantanious fuel consumption, I realize that fuel consumption is very high during acceleration and going uphill, but this energy cannot be recovered well when slowing down or going downhill.
- Mechanical all wheel drive with driveshafts splitting up to all wheels and varying traction control is very sophisticated, but also complex.

The Cross Coupe concept looks simple and neat:
- engine drives front wheels
- electric motors/generators on the rear wheels can provide all-wheel-drive and energy recovery.
- the electric motors can assist acceleration. Electric motors have a high torque to power ratio, which would be beneficial to assist acceleration of a downsized engine, further reducing fuel consumption.
What I do not care so much about at this stage is all electric drive and pluginhybrid.

Other examples of this concept are: Lexus RX450h, Peugeot 3008 and Citroen DS5 Hybrid4.
Quote:
Originally Posted by bigblackwolf View Post
I am not talking about just adding hybrid to an existing car, because that is expensive, but about engine downsizing and eliminating mechanical all-wheel drive, and then adding hybrid.

Audi Q5 has options for different engines, all-wheel-drive and hybrid. So let us look what it costs (price list from Germany).

Cost saving:
Engine downsize and eliminate all-wheel-drive: compare 6-cylinder 3.0TDI quattro 49'200Euro (torque 500Nm) with 4-cylinder 2.0TDI 34'850Euro (torque 320Nm).
Saving: about 14'000Euro.

Additional hybrid cost:
Compare 2.0 TFSI quattro 43'900Euro with 2.0TFSI quattro hybrid 53700Euro. Electro motor has a torque of 210Nm.
Additional cost: 10'000Euro.

So in total, there is still a saving, and the torque loss of the engine downsizing is compensated by the electric motor torque.
It is really difficult to relate engine torque to electric motor torque. Their characteristics are completely different! A gas engine has a relatively constant torque at its operating RPM will a drop off at the beginning and end. An electric motor has maximum torque at 0 RPM and 0 torque at maximum RPM. To further complicate matters transmissions multiple torque and divide RPM. The 1st gear in the X3 28i multiplies the engine's torque by 17.6 times... mean that it is really difficult to discern the value of an engine's torque without understand its RPM range and transmission function. A multi-mode hybrid transmission is even more complicated!

You almost certainly never obtain maximum engine and motor torque at the same time. And as I said earlier the way complicated hybrid transmissions decouple the speeds of a motor and engine it is impossible to interpret their effect without understanding the system better.
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      02-02-2012, 04:17 AM   #7
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How about a Peugeot Hybrid 4. Diesel engine for the from wheels, electric motor for the rear wheels. It can run on diesel or electric or both for 4x4.
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      02-02-2012, 04:23 AM   #8
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The new MDX is rumored to be getting a system like that.

http://www.autoguide.com/auto-news/2...al-clutch.html

Wish it were RWD with the two electric motors for the front wheels though, not a big fan of the current fwd bias of the sh-awd system. The sport hybrid sh-awd in the new NSX may be setup this way but it's rumored to stay mid-engined which would make more sense for the electic motors to be up front.
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      02-02-2012, 04:55 AM   #9
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Hub-mounted electric motors are a terrible idea... Too much weight, too much bulk, no transmission.
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      02-02-2012, 07:21 AM   #10
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I think a good rule of thumb in regards to diesel vs hybrid is diesel is best for highway commutes, hybrid is best for stop and go city driving.

In my mind if you only travel less than 50 miles a day around town then a hybrid or even electric is the way to go; likewise, if you have long commutes on the open road nothing will beat a diesel.
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      02-02-2012, 08:19 PM   #11
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Quote:
Originally Posted by n55x3 View Post
I think a good rule of thumb in regards to diesel vs hybrid is diesel is best for highway commutes, hybrid is best for stop and go city driving.
In my mind if you only travel less than 50 miles a day around town then a hybrid or even electric is the way to go; likewise, if you have long commutes on the open road nothing will beat a diesel.
The discussion which I initially started was not diesel vs hybrid. Diesel can always be applied independent of hybrid, see Peugeot and Citroen. The choice diesel vs petrol is governed by other factors.

The point I raised was a comparison between:
- large size engine and mechanical all-wheel-drive
and
- engine downsizing and all-wheel-drive hybrid.

Even in the case of a long commute drive on open road, I wonder if it would make sense to downsize the engine and integrate an electric motor/generator in the gearbox (the 8speed ZF gearbox is already designed for that as a future option). The downsizing lowers fuel consumption for the long commute and hopefully lowers the capital cost to compensate for the hybrid cost. Again, this is independent of diesel vs petrol.

Or put in a different way:
Step 1: downsize from 6-cylinder 3liter N52 28i to 4-cylinder 2liter N20 28i, and compensate with turbo.
Step2: downsize more and compensate with hybrid.
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      02-03-2012, 03:06 AM   #12
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Quote:
Originally Posted by bigblackwolf View Post
Recently I read about the Volkswagen Cross Coupe concept, and that looks like the kind of technology I would like to have in a future X3.
http://www.topspeed.com/cars/volkswa...-ar120772.html
My interest is based on the following two factors in present technology:
- fuel consumption. When driving the X3 which shows the instantanious fuel consumption, I realize that fuel consumption is very high during acceleration and going uphill, but this energy cannot be recovered well when slowing down or going downhill.
- Mechanical all wheel drive with driveshafts splitting up to all wheels and varying traction control is very sophisticated, but also complex.

The Cross Coupe concept looks simple and neat:
- engine drives front wheels
- electric motors/generators on the rear wheels can provide all-wheel-drive and energy recovery.
- the electric motors can assist acceleration. Electric motors have a high torque to power ratio, which would be beneficial to assist acceleration of a downsized engine, further reducing fuel consumption.
What I do not care so much about at this stage is all electric drive and pluginhybrid.

Other examples of this concept are: Lexus RX450h, Peugeot 3008 and Citroen DS5 Hybrid4.
I am afraid "Hybrids" are just a "Con" they have been proven to be far less economical that any good diesel and less powerful.
Take LEXUS, they said the 450H would be far more economical than my X6 35D M Sport, so I did 60 miles in each over the same roads at the same speeds on the same day. Guess that what, the X6 was quicker and more economical and twice the weight!!!!
Hybrids are just a government "Green brigade" CON.
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      02-03-2012, 04:05 AM   #13
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I'm pretty sure that the Prius is an economically valid purchase. All other hybrid, probably not.
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      02-03-2012, 06:09 AM   #14
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Quote:
Originally Posted by paul386 View Post
I'm pretty sure that the Prius is an economically valid purchase. All other hybrid, probably not.
The following report also shows good figures for the Prius.
http://editorial.autos.msn.com/artic...umentid=435406

Why does the Prius gets it right?
I have the impression that the Prius engine is tuned for efficiency, having compression ratio 13.0 (X3 petrol 10.2 to 11.0) which I think is high for a petrol engine. But the 1.8liter engine only has 142Nm.
Compare that to a Volkswagen Passat 1.8liter TSI which has 250Nm because of a turbo, but for sure also has a lower compression ratio because of the turbocharging in order to avoid knocking.
So the Prius engine can be considered downsized, being tuned for efficiency and not for power, and the electric engine assist acceleration, and recovers braking energy?
Is that the recipe?
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      02-03-2012, 09:31 AM   #15
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The Prius works in the city but thats about it.

Did anyone see the Topgear test of the Prius on their track, the Prius went round as fast as it could being followed by a M3. Result, Prius 17mpg, M3 18mpg. I know it is an extream case but who would think a M3 would be better.

If you want an economy car then get a small diesel plus you are on the wrong forum!
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      02-03-2012, 10:25 AM   #16
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Quote:
Originally Posted by troggy1969 View Post
The Prius works in the city but thats about it.

Did anyone see the Topgear test of the Prius on their track, the Prius went round as fast as it could being followed by a M3. Result, Prius 17mpg, M3 18mpg. I know it is an extream case but who would think a M3 would be better.

If you want an economy car then get a small diesel plus you are on the wrong forum!
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      02-04-2012, 07:43 PM   #17
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Quote:
Originally Posted by troggy1969 View Post
If you want an economy car then get a small diesel plus you are on the wrong forum!
Originally I had intended to make it a thread with a wishlist for technical features in a future X3. But the thread developed in a direction where it would better belong in the universal forum of xbimmers. A site administrator could perhaps move it.

I like a good technical discussion. So when comments are made about getting a diesel instead of downsized engine with hybrid for a future car, I thought about that and I must say I am not sure about diesel technology in future.
Emission limits will get lower and lower, and in the near future, a diesel engine might have to use a combination of:
- SCR selective catalytic reduction, using adblue urea (NOx reduction)
- a diesel particulate filter with a regenerative burner
- an oxidation catalyst to reduce volatile hydrcarbons.
An engineer from a large American company once told me that the emission technology could cost as much as the engine itself, and fuel consumption increases.
In the past, a direct injection turbo diesel without emission technology was attractive form a cost point of view.
But for a future car, I am not sure about diesel.
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      02-04-2012, 08:14 PM   #18
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One thing most greenies don't consider is the total carbon footprint of hybrids. One should consider the energy and resources required to create and dispose on the batteries. Also the electrical generation source is often ignored.

I'd bet if you removed the batteries and electric apputenances from the prius it would likely achieve the same economy because of the reduced weight alone.

Anyway I wish diesels were available in NA.
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      02-04-2012, 08:53 PM   #19
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Quote:
Originally Posted by lbjgh View Post
One thing most greenies don't consider is the total carbon footprint of hybrids. One should consider the energy and resources required to create and dispose on the batteries. Also the electrical generation source is often ignored.

I'd bet if you removed the batteries and electric apputenances from the prius it would likely achieve the same economy because of the reduced weight alone.

Anyway I wish diesels were available in NA.
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      02-05-2012, 04:02 AM   #20
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Quote:
Originally Posted by paul386 View Post
I'm pretty sure that the Prius is an economically valid purchase. All other hybrid, probably not.
In the US maybe here in the UK they are not. Again Diesel power wins, I wish you guys could get the Diesel alternatives over there you would be so sup
surprised.
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      02-05-2012, 07:29 AM   #21
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More diesels and touring models. Dunno why there's not more interest here.
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      02-05-2012, 10:03 AM   #22
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I read a thread from Scott26 who stated that the diesel would be available to North Americans by the end of 2012.

Perhaps the N20 isn't the only engine option change for MY2013. I can only hope at this point! I drove the 3L VW turbo diesel in the Touareg and it was very impressive.

When checking out the MB GLK350 the sales associate told me that in Canada, diesel powered cars accounted for 80% of the sales in any model line offered with Diesels.

VW sells every diesel car they bring into Canada... Lets hope Scott26 is correct and we'll see the oil burner in the X3.

Quote:
Originally Posted by johnbmw6 View Post
In the US maybe here in the UK they are not. Again Diesel power wins, I wish you guys could get the Diesel alternatives over there you would be so sup
surprised.
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